Post date: October 4, 2020
Student: Yuan Hu
Faculty: Timothy S. Fisher
Sponsor: YTC America

Summary: This work reports a low-cost custom electrochemical instrument capable of performing rapid and accurate electrochemical impedance spectroscopy (EIS) for supercapacitors over a broad frequency band (10 mHz to 2 kHz). Conventionally, EIS is measured via sinusoidal perturbations; however, such an approach suffers from lengthy measurement time. Chirp signals have been shown previously to reduce EIS measurement time for supercapacitors for relative narrow frequency bands (1 Hz to 2 kHz). However, to characterize supercapacitors comprehensively, much broader frequency bands are required. Here, we present a custom instrument with an adaptive measurement algorithm for performing EIS measurements in a wide frequency range of 10 mHz to 2 kHz with low measurement uncertainties. The results obtained using this new technique has been validated here with a commercial instrument on several types of supercapacitors. Furthermore, measurement time on average decreases from 1500 s to less than 400 s. The overall cost of the custom instrument is 90% lower as compared to the commercial instrument. The custom instrument’s accuracy, time efficiency and low cost are expected to benefit electrochemical researchers.

(Left) Schematic of the circuit for current measurement. The shaded area indicates resistor bank, which connects an appropriate shunt resistor to the circuit via a signal relay. (Right) EIS measurement results for ACN samples: (A)–(B) Impedance and phase results for ACN sample 1. (C)–(D) Impedance and phase results for ACN sample 2. (E)–(F) Impedance and phase results for ACN sample 3.

Reference:
Hu, Yuan, et al. “Rapid analytical instrumentation for electrochemical impedance spectroscopy measurements.” Journal of The Electrochemical Society 167.2 (2020): 027545.